You know, I just don't think the "leak" was as bold as most people say, for several reasons.
- The leak stated that all 6 chars would be revealed at E3, which they weren't...
- The leak did not say Villager, it said "guy from animal crossing".
- Megaman and Tom Nook were hugely popular in internet posts before Brawl, and then again before SSB4.
- The 3 non-confirmed characters are REALLY obvious choices, based on the number of internet posts about them.
- That leaves WFT, and the fact that the post got her name right, as the only real surprising thing in that entire post.
So taking that the leak was 50% correct, using 5 fairly obvious characters (based on the number of internet posts about each of them) and 1 oddball, that leads me to draw one of a couple conclusions.
Option 1, it was a complete guess, and he got lucky. This is a fairly low possibility, but you can't ignore that it is possible, given the fact that the post was only 50% correct and listed a wrong name for one of the 'correct' characters.
Option 2, the poster did have leaked info on the 3 revealed e3 characters, and filled it in with the other 3 for fun. This is probably the most likely scenario for having gotten the WFT guess right, but it doesn't really explain the wrong name for Villager. This would lead me to believe that it was info passed on from somebody who knew, rather than the poster having actually seen the video, etc.
Option 3, the leak was 100% correct, but Nintendo changed plans of revealing the other 3 for whatever reason. I don't see this as incredibly likely, because Nintendo really needed some hype coming out of this e3, so they could have used the extra Smash Bros help. I certainly don't think they would have changed plans because a handful of people on the internet knew about the leak...
Overall I'm inclined to believe Option 2, even if the other 3 characters are confirmed at a later date... but I'm definitely against people who say "because he got this part right, the rest has to be right"